At least 16 perish in Texas balloon fireball horror

Law enforcement officers examine the scene of a hot air balloon crash that killed 16 people in Maxwell, Texas, U.S. July 30, 2016. Rodolfo Gonzalez/Austin American-Statesman/via REUTERSInvestigators use a drone to examine the site of a balloon crash and explosion that left 16 feared dead near Maxwell, Texas, U.S. July 30, 2016. REUTERS/Robin JerstadAuthorities head down a dirt road toward to investigate the scene of a hot air balloon crash that left 16 feared dead near Maxwell, Texas, U.S. July 30, 2016. REUTERS/Robin JerstadCaldwell County Sheriff's deputies block off the road to the site where a hot air balloon caught fire and crashed leaving 16 feared dead near Maxwell, Texas, U.S. July 30, 2016. REUTERS/Robin JerstadLaw enforcement officers examine the scene of a hot air balloon crash that killed 16 people in Maxwell, Texas, U.S. July 30, 2016. Rodolfo Gonzalez/Austin American-Statesman/via REUTERSThe partial frame of a hot air balloon is visible above a crop field as investigators comb the wreckage of a crash Saturday morning, July 30, 2016, near XXX, Texas. Authorities say the accident caused a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)Local resident Margaret Wylie describes a burst of flames she saw in the field across the road from her house at the scene of a hot air balloon crash near Lockhart, Texas, Saturday, July 30, 2016, causing what authorities described as a "significant loss of life."(Ralph Barrera/Austin American-Statesman via AP)Texas DPS Trooper Robbie Barrera, center right, puts her arm around Caldwell County Sheriff Daniel Law as he arrives on the scene of a hot air balloon crash Saturday, July 30, 2016 near Lockhart, Texas, causing what authorities described as a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)A drone is seen flying as first responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)The partial frame of a hot air balloon is visible above a crop field as investigators comb the wreckage of a crash Saturday morning, July 30, 2016, near Lockhart, Texas. Authorities say the accident caused a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)In this aerial photo authorities investigate after a hot air balloon caught on fire and crashed in in Central Texas near Lockhart, Texas, Saturday, July 30, 2016, causing what authorities described as a "significant loss of life." (Rodolfo Gonzalez/Austin American-Statesman via AP)First responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)First responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)The partial frame of a hot air balloon is visible above a crop field as investigators comb the wreckage of a crash Saturday morning, July 30, 2016, near XXX, Texas. Authorities say the accident caused a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)

A top-level government investigation has begun after at least 16 people on board a hot air balloon were believed to have been killed when it caught fire and crashed in Texas.

Authorities would not confirm the exact number of deaths, but Lynn Lunsford of the Federal Aviation Administration said the balloon was carrying at least 16 people and Caldwell County Sheriff's Office said it did not look like anyone survived.

If the death toll is correct, it is one of the worst such disasters and possibly the worst in US history.

The deadliest such accident happened in February 2013, when a balloon flying over Luxor, Egypt, caught fire and plunged 1,000 feet to the ground, crashing into a sugar cane field and killing at least 19 foreign tourists

Saturday's Texas crash happened at about 7.40am local time in a pasture near Lockhart, about 30 miles south of Austin. The land near the crash site is mostly farmland, with corn crops and grazing cattle.

Cutting through that farmland is a row of massive high-capacity electrical transmission lines about four to five storeys tall. The site of the crash appears to be right below the overhead lines, though authorities have not provided further details about what happened. Aerial photos showed an area of charred pasture underneath power lines.

Local resident Margaret Wylie describes a burst of flames she saw in the field across the road from her house at the scene of a hot air balloon crash near Lockhart, Texas, Saturday, July 30, 2016, causing what authorities described as a "significant loss of life."(Ralph Barrera/Austin American-Statesman via AP)Texas DPS Trooper Robbie Barrera, center right, puts her arm around Caldwell County Sheriff Daniel Law as he arrives on the scene of a hot air balloon crash Saturday, July 30, 2016 near Lockhart, Texas, causing what authorities described as a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)A drone is seen flying as first responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)The partial frame of a hot air balloon is visible above a crop field as investigators comb the wreckage of a crash Saturday morning, July 30, 2016, near Lockhart, Texas. Authorities say the accident caused a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)In this aerial photo authorities investigate after a hot air balloon caught on fire and crashed in in Central Texas near Lockhart, Texas, Saturday, July 30, 2016, causing what authorities described as a "significant loss of life." (Rodolfo Gonzalez/Austin American-Statesman via AP)First responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)First responders and investigators appear at a scene of a balloon crash that reports indicate took the lives of 16 people near Maxwell, Texas in Caldwell County Saturday, July 30, 2016. (Kin Man Hui/The San Antonio Express-News via AP)The partial frame of a hot air balloon is visible above a crop field as investigators comb the wreckage of a crash Saturday morning, July 30, 2016, near XXX, Texas. Authorities say the accident caused a "significant loss of life." (Ralph Barrera/Austin American-Statesman via AP)

Margaret Wylie, who lives about a quarter of a mile from the crash site, said she was letting her dog out when she heard a "pop, pop, pop".

"I looked around and it was like a fireball going up," she said, noting that the fire was under large power lines and almost high enough to reach the bottom of them.

Ms Wylie, who called 911, said the weather seemed clear and that she frequently saw hot air balloons in the area.

Erik Grosof of the National Transportation Safety Board said the agency deemed it a major accident and a full investigation would begin on Sunday when more national officials arrive.

"This will be a difficult site for us to work through," Mr Grosof said.

The balloon was operated by Heart of Texas Hot Air Balloon Rides, according to two officials familiar with the investigation.

Heart of Texas' website says it offers rides in the San Antonio, Houston and Austin areas.

The company's Facebook page features photos of a hot air balloon with a smiley face with sunglasses on it up in the air, people waving from a large basket on the ground and group selfies taken while up in the air.

The operation does not appear to be registered with the state of Texas.

Authorities have not released the names of those who were on board and have not said who was flying the balloon, but Skip Nichols identifies himself on his Facebook page as the chief pilot of Heart of Texas and pictures posted by him are on the business' Facebook page.

Mr Nichols, 49, is also the registered owner of Missouri-based Air Balloon Sports. No-one answered the door at a home in Kyle, Texas, believed to be his, calls to Heart of Texas operations manager Sarah Nichols, 72, rang unanswered, and a woman in Missouri believed to be his sister did not return calls seeking comment.

Warning about potential high-fatality accidents, safety investigators recommended two years ago that the Federal Aviation Administration impose greater oversight on commercial hot air balloon operators, US government documents show. The FAA rejected those recommendations.

In a letter to FAA Administrator Michael Huerta in April 2014, the National Transportation Safety Board urged the FAA to require tour companies to get agency permission to operate, and to make balloon operators subject to FAA safety inspections.

Mr Huerta responded that regulations were unnecessary because the risks were too low.

After his reply, the NTSB classified the FAA's response to the two balloon safety recommendations as "open-unacceptable", which means the safety board was not satisfied with the FAA's response.

Speaking just before leaving for Texas to lead the crash investigation, NTSB board member Robert Sumwalt said he was studying the board's recommendations from previous hot air balloon accidents.

"I think the fact that it is open-unacceptable pretty much speaks for itself," he said.

He also noted that the team was still trying to gather basic information about the accident.

Ms Lunsford said it was difficult to say whether the Texas crash would cause the agency to reconsider NTSB's recommendations "until we've had a chance to gather and examine the evidence in this particular case".